Hormonal response patterns are differentially influenced by physical conditioning programs during basic military training

Abstract

Objectives: Compare traditional military physical training and more contemporary physical training on catabolic and anabolic hormones and body composition in recruits undertaking basic military training (BMT).

Design: A prospective cross-sectional study design.

Methods: Two recruit intakes were assessed over the 12-week Australian Army BMT course. The control group (CON) comprised 40 recruits (26M/14F) and the experimental group (EXP) comprised 35 recruits (25M/10F). Hormone concentrations (IGF-I, testosterone, cortisol, SHBG) and body composition were assessed at weeks 1 and 12. The EXP group undertook a higher-load/intensity physical training regimen, while CON undertook the extant physical training program which focused on cardiovascular and muscular endurance. Total physical activity within physical training sessions was assessed during weeks 2, 6 and 9.

Results: There was a significant group×time interaction (p<0.01) for IGF-I and cortisol, and main effects over time (p<0.01) for IGF-I, cortisol and SHBG. There were main effects for time (p<0.05) for lean and fat mass, and these changes were associated (p<0.05) with altered hormone concentrations. Physical activity levels were approximately 50% lower in EXP than CON during physical training sessions.

Conclusions: This is the first study to report a differential hormone response to contrasting physical conditioning regimen during BMT. The results indicate that the recruits who completed the EXP physical training regimen had an attenuated stress profile. This is an important observation, as any enhancement of recruit training outcomes are critical for Army noting that fundamentally, organisational capability is reliant upon the physical capability of its personnel.

Keywords: Exercise physiology; Hormones; Military; Physical training.